Original Article Effects of aromatherapy essential oil inhalation on the stress response after exposure to noise and arithmetic subtraction ...
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
Int J Clin Exp Med 2018;11(1):275-284
www.ijcem.com /ISSN:1940-5901/IJCEM0051785
Original Article
Effects of aromatherapy essential oil inhalation on the
stress response after exposure to noise and arithmetic
subtraction stressor: randomized controlled trial
Iklyul Bae1*, Ji-Ah Song1*, Mikyoung Lee2, Myunghaeng Hur2
1
Konyang University, Daejeon, South Korea; 2Eulji University, Daejeon, South Korea. *Equal contributors.
Received January 15, 2016; Accepted October 7, 2017; Epub January 15, 2018; Published January 30, 2018
Abstract: Objective: This study used a nonequivalent control group pretest/posttest design in order to compare the
effects of aromatherapy essential oil (EO) inhalation on psychological and physiological responses after exposure
to stressors. Methods: This study was a Randomized single Blind Controlled Trial. A total of 95 individuals who met
the selection criteria were included as research subjects, and divided into experimental (n=33), placebo (n=31),
and control (n=31) groups. In order to determine the effects of aromatherapy EO inhalation, subjects were asked a
series of repeated arithmetic subtraction problems, in which they subtracted increments of 17 from 6315 for 2 min
following a stressor: 3 min of white noise using a headset. The experimental group was inhaled 2 drops (2 drops=0.1
cc) of the blended EO of Lavandular officinalis and Cananga odorata, placebo group, 2 drops of 0.9% saline solu-
tion; and control group, no inhalation. Measurements of stress scores, stress index, sympathetic nerve activity,
serum cortisol levels, and blood pressure were examined in 4 test sessions: prior to the experiment (pre-test), right
after exposure to the stressor, 10 min after the experiment, and 30 min after the experiment. Results: The stress
index showed significant differences among the three groups (F=4.546, P=.013). Sympathetic nerve activity also
showed significant differences among the three groups (F=6.056, P=.003), while cortisol levels were only partially
significantly different among the three groups (F=3.110, P=.049). Both systolic (F=4.380, P=.015) and diastolic
(F=4.438, P=.014) blood pressure readings showed significant between-group differences. Conclusion: The inhala-
tion of aromatherapy EO was effective in reducing the stress score, stress index, sympathetic nerve activity, serum
cortisol level, and blood pressure of participants.
Keywords: Stress, noise, essential oil, sympathetic nerve, cortisol, blood pressure
Introduction mus-pituitary-adrenal response [3]. According
to a study by Lee, Hwang, and Kim [4], exces-
Stress is emerging as an important issue sive excretion of cortisol from persistent and
in modern society. Appropriate regulation of excessive stress can cause diverse problems
stress is a vital element in improving one’s associated with the cardiovascular, digestive,
health, although individuals manifest varied and musculoskeletal systems, and cause lost
responses to both routine and diverse stress- homeostasis and emotional stability. It can also
inducing factors [1]. cause disease as an ineffective stress coping
mechanism.
Long-term stress can induce physiological
responses, including autonomic nervous sys- As such, there is an increasing interest in non-
tem (ANS) responses from stimulation of the pharmacological treatments without adverse
hypothalamus by the cerebral cortex, and the effects as intervention measures for stress
activated sympathetic nervous system releas- relief [5]. With the recent surge in interest in
ing catecholamines [2]. As a result, blood pres- complementary and alternative medicine (CAM)
sure and heart rate increase and cortisol is therapies, comprehensive care for stress inter-
released into the blood vessels by a hypothala- vention is being emphasized [6]. There have
Effects of aromatherapy on stress response
Figure 1. Study design.
been previous studies on the effects of abdom- diseases or to pretest/posttest evaluations on
inal massage for providing stress relief [7], the experimental treatments.
effects of hand massage on stress responses
[4], and the efficacy of aromatherapy on stress Thus, the present study was conducted on
[8]. Massage therapies, as many have pointed healthy adults, in order to investigate interven-
out, are limited by the need for skilled practitio- tion effects on both relief and prevention of
ners to perform the massage [9], as well as dif- stress induced after exposure to noise and
ficulties in sustaining the therapy on an individ- arithmetic subtraction stressor. Moreover, for
ual basis due to the need for separate spaces the development of scientific and objective
and/or equipment [7]. nursing interventions, environmental effects
were minimized and, as a measure to control
On the other hand, inhalation of essential oil exogenous variables, the study was conducted
(EO) involves both short application times and in a laboratory with constant environmental
quick physical response in patients, with EO settings. Furthermore, by identifying the effects
components being detected in blood within 5 of EO inhalation on stress over time, we could
min and reaching maximum levels within 20 better investigate its time-based anti-stress
min. It is a non-invasive method that affects the effects.
brain directly, is a CAM therapy that is not
restricted by time or place, is fast acting, and Participants and methods
shows virtually no adverse effects [5]. Further,
this method has an outstanding efficacy, as it Study design
spreads to the entire body through respiration
to induce chemical reactions with enzymes, The present study used a parallel control group
brings about enhanced psychological and phys- non-synchronized design to examine the effects
ical relief effects [10], and can positively affect of EO inhalation on stress index, sympathetic/
blood flow [11]. parasympathetic nerve activities, cortisol, and
blood pressure after exposure to noise and
Earlier studies on stress intervention using arithmetic subtraction stressor (Figure 1).
aroma inhalation have examined its effects on
blood pressure and stress response in patients Participants
with essential hypertension [9], its effects on
physical resistance to ANS and stress in The study participants consisted of those who
patients after stroke [12], and its effects onpa- were recruited volunteers between July and
tients with breast cancer receiving radiation September 2013. Selection criteria included
therapy [13]. However, many of these studies understanding the study objectives and volun-
were limited either to participants with various teering to participate; male and female adults
276 Int J Clin Exp Med 2018;11(1):275-284Effects of aromatherapy on stress response
Figure 2. Flow chart for (4) Data were collected from
participant recruitment. the control, placebo, and
experimental group, in order,
as part of a non-synchro-
nized design.
(5) The data ID was codified
to numbers and analyzed
anonymously following data
collection.
Concealment and blinding
After securing a list of partici-
pants through the recruit-
ment announcement, the
experimental, placebo, and
control groups were random-
ly assigned. As a non-syn-
chronized design, data were
collected from the control
group first, followed by the
placebo group and then the
experimental group. After
group assignment, the par-
ticipants were not given any
information regarding their
group assignment.
between the ages 20 and 35 years and exclu- Sample size calculation
sion criteria were suffering from rhinitis, asth-
ma, or cold that could affect sense of smell. Sample size was obtained by inputting alpha
Individuals who were currently receiving treat- value, statistical power, and effect size into
ments for physical or mental conditions or who theG-power 3.1.7 program (Heinrich Heine
were taking anxiolytics or hypnotic medications University, Dusseldorf, Germany). To compare
were excluded. the differences between the three groups,
effect size was calculated, based on a previous
Data were collected in accordance with the fol- study [9], by inputting the number of groups,
lowing procedures. standard deviation, and mean, which resulted
in an effect size of .34. The sample size was
(1) Candidates were recruited through an calculated with the effect size, significance
announcement, and selections made after veri- level (α), and the power (1-β), .34, .05, and .9,
fying the status on any diseases and medica- respectively into the formula, it was determined
tions taken. that the total sample size needed was 90. In
the present study, the total number of partici-
(2) Explanations on experimental treatment, pants was 99, allowing for a 10% drop-out rate,
investigation methods, self-determination, and and the experimental, control, and placebo
self-withdrawal were given to the candidates, groups were assigned 33 participants each.
and signed consent forms were received from However, 2 people in the control group dropped
those consenting to participate. out owing to problems in securing an IV line,
and 2 in the placebo group dropped out: one for
(3) The MS Excel program (Microsoft, Redmond, inability to take the treatment medication and
Wash) was used to randomly assigned partici- the other for inability to participate in the exper-
pants to the experimental, placebo, and control iment. Therefore, the final number of partici-
groups. pants was 95: with 33, 31, and 31 participants
277 Int J Clin Exp Med 2018;11(1):275-284Effects of aromatherapy on stress response
in the experimental, control, and placebo the systolic and diastolic pressures. Mea-
groups, respectively (Figure 2). surements were taken from the upper arm in a
sitting position after the participants were
Outcome measures stabilized.
Stress index Laboratory preferences
The stress index represents the value for stress The area of the laboratory was 19.83 m2, and
conditions based on balance of the ANS derived the temperature inside the measurement site
from heart rate variability (HRV) measured con- was set to 22 to 24°C, which was considered to
tinuously for 5 min using the Canopy 9 profes- be the appropriate temperature for the human
sional 4.0 (IEMBIO, Gangwon-do, Korea), an body, as well as for measuring ANS response
ANS measurement instrument. The stress and blood pressure. The laboratory was well-
index is based on a scale of 1 to 10, with higher ventilated, and the measurement site was fur-
scores indicating greater exposures to stress nished with a sofa, a table, and chairs to pro-
conditions. vide a comfortable environment for the
participants.
Low frequency activity
Intervention
Sympathetic nerve activity was measured by
low frequency activity of HRV which is the value Stressor
representing the area of low frequency (LF), as
a sympathetic nerve index. This was calculated White noise refers to a series of noises with a
from the value using HRV, measured continu- frequency that is distributed in a continuously
ously for 5 min with Canopy 9 professional 4.0. uniform manner throughout the entire audible
Higher sympathetic nerve activity values indi- range of 20 to 20.000 Hz, as well as fixed
cate greater exposures to stress conditions. sounds that do not have specific audible pat-
terns. As white noise has been found to have
Serum cortisol
negative effects on mental arithmetic opera-
Cortisol is a response variable for stress. Thus, tions, as well as physical and mental health, it
our experiments were conducted between 4 was effectively used as the stressor. Based on
pm and 7 pm, when cortisol variability is low- the results from a previous study [14], the par-
est. In order to minimize the influence of exter- ticipants had heard 70 dB white noise for 3 min
nal factors on cortisol, minimizing smoking, through headphones (MDR-1R, Sony Corpo-
controlling diet, and other precautions were an- ration, Tokyo Japan) as astressor, after which,
nounced in advance, and compliance was veri- as a stress stimulus via mental arithmetic oper-
fied with all participants before administering ations, they were instructed to perform sub-
experimental treatments. tractions, starting from 6,135 and continuously
subtracting 17 from the resultant, for 2 min. If
To measure serum cortisol levels, a nurse per- an incorrect answer was given, they were
formed a venipuncture; after which, a 3-way instructed to start over from the beginning.
syringe stopcock was used to secure a vein in
order to draw 3 mL of venous blood. The col- EO selection
lected blood was centrifuged in a well-equipped
laboratory and then cold-stored. Then, the sp- Based on the results from a study by Oh [10],
ecimens were sent to laboratories for analysis which reported that blending 2 to 3 aroma EOs
of a cortisol with Cobra 5010 Quantun analysis with similar effects maximizes their synergistic
equipment (Packard Instrument Co., Meridian, effects, as well as advice from experts that
Conn); the unit of analysis was mcg/dL. have completed international aromatherapy
certifications, oils that affect stress and ANS
Blood pressure [15] were selected and blended. Accordingly,
the oils used in the present study were
For measurement of participants’ blood pres- Lavandular officinalis, which has effects on
sure, an electronic blood pressure monitor subduing excitation of the heart, reducing blood
(Omron IA2, Kyoto, Japan) was used to measure pressure, and treating hypertension and heart
278 Int J Clin Exp Med 2018;11(1):275-284Effects of aromatherapy on stress response
Table 1. Homogeneity test on general characteristics of participants
Exp. (n=33) Plac. (n=31) Cont. (n=31)
Characteristics/Variable Category F/X2 P
Mean ± SD or N (%) Mean ± SD or N (%) Mean ± SD or N (%)
Age (yr) 21.45±1.94 21.06±1.98 21.74±1.67 1.024 .363
Height (cm) 163.91±6.73 163.48±7.42 165.61±8.08 0.718 .491
Body weight (kg) 57.21±11.05 55.06±8.79 58.23±11.21 0.744 .478
Gender Male 5 (15.2) 7 (22.6) 9 (29) 1.795 .408
Female 28 (84.8) 24 (77.4) 22 (71)
Drinking alcohol No 20 (60.6) 14 (45.2) 20 (64.5) 2.659 .265
Yes 13 (39.4) 17 (54.8) 11 (35.5)
Smoking No 31 (93.9) 30 (96.8) 26 (83.9) 3.712 .156
Yes 2 (6.1) 1 (3.2) 5 (16.1)
Initial Stress Index 2.67±1.51 3.26±1.94 2.48±1.45 1.867 .160
Initial LF activity 5.42±0.58 5.70±0.68 5.83±1.08 2.090 .130
Initial Cortisol (mcg/dL) 7.65±3.64 8.15±4.54 6.85±2.80 0.957 .388
Initial SBP (mmHg) 114.85±10.35 116.06±10.15 115.90±12.10 0.250 .779
Initial DBP (mmHg) 72.64±8.92 72.81±5.81 72.67±6.94 0.105 .901
Exp.: Experimental group, Plac.: Placebo group, Cont.: Control group. Mean ± SD: Mean ± Standard Deviation. SBP: Systolic
Blood Pressure. DBP: Diastolic Blood Pressure. LF: Low Frequency.
palpitations, and Cananga odorata which is and placed 10 cm away from the participant’s
effective in reducing blood pressure, relieving nose for 10 min of inhalation in a comfortable
heart palpitations and nervous tension, and position.
mental relaxation. Lavandular officinalis and
Cananga odorata were blended at a 1:1 ratio The placebo group
and cold-stored before use.
After loading the stressor, each participant was
stabilized comfortably, followed by inhalation of
Data collection
a 0.9% saline. The inhalation method was the
same as the experimental group.
Pre-surveys (T0): In terms of study procedures,
pre-surveys were conducted when the partici- The control group
pants first visited the laboratory. After partici-
pants seated in a chair for 5 min to be stabi- After loading the stressor, each participant was
lized, an IV line was secured, using a 3-way stabilized comfortably for 10 min.
syringe stopcock for blood collection, followed
by another 5 min for stabilization. After the Post-survey (T10, T30)
stress score was measured, blood pressure The first post-survey (T10) was performed 10
was also monitored. We measured both stress minutes after the experiment and the second
index and sympathetic/parasympathetic nerve post-survey (T30) was performed 30 minutes
activities, and then collected and stored 3 mL after the experiment. Stress scores, blood
of venous blood from each participant. pressure, stress index, and sympathetic/para-
sympathetic activity were measured in each
Experimental treatment
post-surveys. 3 mL of venous blood was col-
lected using a secured 3-way syringe stopcock
The experimental group
and stored in a blood-collection container.
After loading the stressor, each participant was Afterwards, the participants were instructed to
stabilized comfortably, followed by EO inhala- complete the post-survey questionnaire.
tion. In terms of the inhalation method, two Ethical considerations
drops of cold-stored EO (2 drops=0.1 cc), a
blend of Lavandular officinalis and Cananga This study was approved (EU 13-17) through
odorata, were dropped onto an aroma stone the institutional review board of our institution.
279 Int J Clin Exp Med 2018;11(1):275-284Effects of aromatherapy on stress response
Table 2. Comparison on stress index, sympathetic/parasympathetic nerve activities, cortisol, systolic/
diastolic blood pressure between the experimental, placebo, and control groups (N=95)
Exp. (n=33) Plac. (n=31) Cont. (n=31)
Variable F P F (p)*
Mean ± SD Mean ± SD Mean ± SD
Stress Index T0 2.67±1.51 3.26±1.94 2.48±1.45 1.867 .160 Time 49.336 (Effects of aromatherapy on stress response
Results blended Lavandular officinalis and Cananga
odorata EO, the placebo group was given 0.9%
We performed a homogeneity pre-test on the saline, and the control group was given nothing
three groups, and confirmed homogeneity, as for inhalation. Measurements were taken at
no significant differences were seen between four points: prior to experimental treatment,
the experimental, placebo, and control groups after presenting the stressor, 10 min after
for general characteristics and dependent vari- treatment, and 30 min after treatment, in order
ables (Table 1). to identify time-based effects.
The four measurements taken for verification of Ward [15] reported that noise has a negative
the effects of EO inhalation on stress index effect on task performance; in a study related
showed significant differences based on time to heart rate, it was reported that exposure to
(F=49.336, PEffects of aromatherapy on stress response
post-treatment. Based on these results, it was tolic blood pressure, the experimental group
confirmed that EO inhalation reduced stress showed a significant decrease compared to the
scores and sympathetic nerve activities to lev- placebo and control groups at both 10 and 30
els prior to inducement of stress, and thus is minutes after treatment. When compared to a
effective in aiding recovery from the stress study that reported a decrease in systolic blood
response. pressure after a 4-week inhalation of blended
lavender and ylangylang EO through necklace
These results are consistent with other studies and aroma stone applications [19], our results
that indicated sympathetic nerve activity was were more effective, time- and cost-wise, as
reduced after aroma EO inhalation [16], and recovery and reduction in systolic blood pres-
that stress scores decreased at 10 minutes sure were seen after just 10 minutes.
after treatment for stress using aroma EO,
blended with lavender, ylangylang, rosemary, It appeared these physically relaxing effects
and lemon [17]. Moreover, when compared to and decreases in sympathetic nerve activities
the study by Nord [6] on the use of single oil, it indicated feelings of stability, which led to a
is believed that using blended EOs shows more decrease in blood pressure. In particular, sys-
synergistic effects that using a single oil in tolic blood pressures measured in the labora-
reducing stress. This is consistent with another tory showed decreases in the experimental
study that reported blending 2 to 3 different group of approximately 9.76 mmHg within 10
oils maximized their efficacy through synergis- minutes and 11.87 mmHg after 30 minutes.
tic effects [18]. This quick decrease in blood pressure from
acute effects of EO inhalation could represent
When the effects of aroma EO inhalation on a meaningful finding. Moreover, diastolic blood
serum cortisol were tested, the results showed pressure showed a significant decrease in the
no significant differences between the three experimental group at 10 minutes after EO
groups at 10 minutes after treatment. However, inhalation, compared to the placebo and con-
at 30 minutes after treatment, significant dif- trol groups, but significant differences were not
ferences between the three groups were seen after 30 minutes. This demonstrated that
observed, with the experimental and placebo inhalation of blended Lavandular officinalis and
groups showing significant decreases in com- Cananga odorata aroma EO had an immediate
parison to the control group. Changes in corti- effect on diastolic blood pressure, but after
sol in the three groups consisted of an increase recovery to a certain level, it stabilized.
in cortisol levels after being subjected to the
stressor and a decrease in serum cortisol at 10 Most of the recent studies on applying aroma
and 30 minutes after treatment in the control EO for studying ANS and blood pressure
group, which only had the stressor removed; involved participants with various diseases,
the experimental group, which had the stressor and relied on pre- and post-experimental treat-
removed and was treated with EO inhalation; ment comparisons. In other words, there are
and the placebo group, which had the stressor virtually no studies conducted on adults who
removed, and was treated with a saline inhala- had not been diagnosed with a disease that
tion. From this, it was indirectly confirmed that examine the effects of aroma EO inhalation.
serum cortisol changes depend on the levels of The present study was conducted in a labora-
stress. However, in the study results, no signifi- tory setting to identify the effects of aroma EO
cant differences between the experimental and inhalation on stress score, stress index, sympa-
placebo groups were discovered. Therefore, in thetic/parasympathetic nerve activities, serum
order to explain the effects of aroma EO inhala- cortisol, and blood pressure in healthy adults.
tion on serum cortisol concentration, further
studies, which supplement additional informa- From a nursing research perspective, it was
tion on frequency and time of inhalation and determined that for aroma EO applications for
the components and types of oil used, are stress relief, blended oils were more effective,
deemed necessary. through synergistic effects, than single oils.
The EO applications had an effect on sympa-
Finally, to investigate the effects of EO inhala- thetic nerve activity and blood pressure, par-
tion on vital signs, systolic and diastolic blood ticularly how they reduced these levels to below
pressures were measured. As a result, for sys- the initial stress values. If future studies on
282 Int J Clin Exp Med 2018;11(1):275-284Effects of aromatherapy on stress response
decreases in blood pressure based on time can and serum immunity of registered nurse dur-
confirm the time frame of stress recovery, EO ing the night duty. J Korean Acad Soc Nurs
inhalation could potentially have broad-based Educ 2007; 13: 169-176.
applications in practical nursing. [5] Rimmer L. The clinical use of aromatherapy in
the reduction of stress. Home Healthc Nurse
Further, the results of this study can contribute 1998; 16: 123-126.
to the development and the utilization of aroma [6] Nord D and Belew J. Effectiveness of the es-
sential oils lavender and ginger in promoting
EO inhalation applications as a CAM therapy
children’s comfort in a perianesthesia setting.
that can be easily used as a relaxation therapy J Perianesth Nurs 2009; 24: 307-312.
in daily life. Indeed, it could potentially serve as [7] Chung M and Choi E. A comparison between
a self-nursing intervention measure for stress effects of aroma massage and meridian mas-
relief for adults, and contribute to enhancing sage on constipation and stress in women col-
both their quality of life and maintenance of lege students. J Korean Acad Nurs 2011; 41:
their health. 26-35.
[8] Park MK and Lee ES. The effect of aroma inha-
In conclusion, aroma EO inhalation was shown lation method on stress responses of nursing
to be effective for stress relief, as it decreased students. Taehan Kanho Hakhoe Chi 2004;
stress score as a psychological response, and 34: 344-351.
reduced stress index, sympathetic nerve activ- [9] Hwang JH. The effects of the inhalation meth-
ity, and blood pressure as a physiological od using essential oils on blood pressure and
stress responses of clients with essential hy-
response. Therefore, it can be used as a meth-
pertension. Taehan Kanho Hakhoe Chi 2006;
od for relieving stress in both clinical and every-
36: 1123-1134.
day settings, in which there are greater expo- [10] Oh HK, Choi JY, Chun KK, Lee JS, Park DK, Choi
sures to diverse stressors. SD, Chun TI, Kim MK and Kim SB. A study for
antistress effects of two aromatic synergic
Acknowledgements blending oils. Proceedings of Korean Jungshin
Science Symposium 2001; 14: 33-49.
This research was supported by Basic Science [11] Battaglia S. The complete guide to aromather-
Research Program through the National Re- apy. International Centre of Holistic Aromather-
search Foundation of Korea (NRF) funded by apy, Australia. Perfect Potion, 2003.
the Ministry of Science, ICT & Future Planning [12] Shin YS, Cho YS and Jung YJ. The effects of
(NRF-2012R1A1A3013176) (NRF-2015R1A1A- aromatherapy on autonomic nerve system and
3A04001441). physical resistance of a stress. JKBNS 2004;
6: 5-17.
Disclosure of conflict of interest [13] Yun SH, Cha JH, Yoo YS, Kim YI, Chung SM and
Jeong HL. Effects of aromatherapy on depres-
None. sion, anxiety and the autonomic nervous sys-
tem in breast cancer patients undergoing adju-
Address correspondence to: Myunghaeng Hur, vant radiotherapy. Korean J Hosp Palliat Care
College of Nursing, Eulji University, 77 Gyeryong-ro, 2012; 15: 68-76.
771 Beon-gil, Jung-gu, Daejeon 34824, South [14] Yoon YH, Kim SH, Lee HJ, Lee JH and Kim HT.
Korea. Tel: 82(0)10-3348-0870; E-mail: mhhur@ The effects of task stressor, noise stimulus, co-
eulji.ac.kr nifer needle odor and soundguard on SCR,
PPG and behavioral performance. Korean
References Journal of Clinical Psychology 1997; 16: 435-
445.
[1] Brunner LS, Smeltzer SCC, Bare BG, Hinkle JL [15] Ward WD and Fricke JE. Noise as a public
and Cheever KH. Brunner & Suddarth’s text- health hazard: proceedings. American Speech
book of medical-surgical nursing. Philadelphia, and Hearing Association, 1969.
Lippincott Williams & Wilkins 2010. [16] SM Peng, Koo M and Yu ZR. Effects of music
[2] Ha BJ. Aromatherapy. Seoul, Soomoonsa, and essential oil inhalation on cardiac auto-
2006. nomic balance in healthy individuals. J Altern
[3] Hal JE. Guyton and Hall textbook of medical Complement Med 2009; 15: 53-57.
physiology. Philadelphia, Saunders Elsevier, [17] Muzzarelli L, Force M and Sebold M. Aroma-
2011. therapy and reducing preprocedural anxiety: a
[4] Lee HS, Hwang HS and Kim YA. Effects of hand controlled prospective study. Gastroenterol
massage with aroma oil on stress responses Nurs 2006; 29: 466-471.
283 Int J Clin Exp Med 2018;11(1):275-284Effects of aromatherapy on stress response
[18] Hongratanaworakit T and Buchbauer G. Relax- sure and salivary cortisol levels in prehyper-
ing effect of ylang ylang oil on humans after tensive and hypertensive subjects. Evid Based
transdermal absorption. Phytother Res 2006; Complement Alternat Med 2012; 2012:
20: 758-763. 984203.
[19] KimI H, Kim C, Seong K, Hur MH, Lim HM and
LeeMS. Essential oil inhalation on blood pres-
284 Int J Clin Exp Med 2018;11(1):275-284You can also read
